Make the host pane something you ask for, and draw it as cards

THE DRAWER USED TO ARRIVE WITH THE SELECTION. IsDrawerOpen read "a host is
selected", so touching any card took 304 pixels off the grid — including every
card arrowed past on the way to the one somebody wanted. Choosing among forty
machines was charged the price of the pane for one of them. A pencil now appears
on the card under the pointer and on the selected card, and that is what opens
it; IsHostPaneOpen is the flag, and the grid's context menu gained Details… so
the pane is reachable without a pointer, which a hover-only control is not.

Once open it follows the selection rather than pinning the host it was opened
on: a pane about one host beside a grid marking a different one is two answers
to the same question. Losing the selection closes it and clears the flag, or a
filter matching nothing would leave the pane armed to spring open again on the
next card merely selected — which is the behaviour the pencil exists to remove.

The pencil is drawn over the card rather than in a column of its own. A column
would have cost the name 30 pixels of a 232-pixel tile, permanently, for a
control that is only there while the pointer is; the dot and the pencil stack in
the two corners of that edge instead. IsVisible and not opacity, because a
button at zero opacity still takes the click and the card underneath does not.

A HEADER, A BODY THAT SCROLLS, AND A FOOTER, which is the one structural change
in the pane. The header names what the drawer is about and carries the two
things true of every panel; the footer carries the one thing each panel is for —
CONNECT, or SAVE, or the question about deleting. Only the middle scrolls, so
the button somebody came here to press can no longer be below the fold, which
CONNECT could be on a host with fifteen tags. That also widens what the layout
harness certifies: it skips anything inside a ScrollViewer, and the control each
panel exists to offer is now outside one.

THE SAME THREE CARDS TWICE. Address, General, Connection — first as rows stating
what the host is, then as boxes for changing it. The detail pane's rows are
buttons that open the editor: the design draws every fact as a filled box, and
rather than draw an input that refuses the pointer, pressing one leads to the
same card with a real box in it. Nothing here saves as you type, and that is not
timidity — saving validates the key-or-credential exclusion and writes one
encrypted payload, so a box committing per keystroke would be a save per
character and a half-typed hostname on the wire.

Every value the pane prints is the resolved one, and says "inherited" beside it
where a group supplied it. The number is the same either way and the edit is
not: clearing a group's default moves every host that never overrode it.

A HOST CARD IS TWO LINES AND NO CHIPS. The subtitle is now "ssh, root, pci,
eu-west-1" — the transport, the resolved account, then every tag — replacing
both the user@host:port line and the wrapped row of tag chips under it. The
address went to the card's tooltip rather than nowhere: a card is read while
scanning forty machines, where the name and the kind of machine are what is
being looked for, and an address is what you read once you have found it.

"ssh" is a constant today and is printed anyway, which is the one thing here
that argues with this codebase's own rule about constants dressed as readings.
It is the first item of a list whose other items vary, and a list beginning with
the account on one card and a tag on the next has no shape to scan. The remark
on HostRowViewModel.Summary says so rather than leaving it to be discovered.

WHAT THE DESIGN DRAWS AND THIS PANE HAS NOT GOT: Share this host, Add Telnet,
"SSH ID, Certificate, FIDO2", the backspace-key mapping row, the vault picker's
chevron and Show more. Sharing is per vault and not per item, every session here
is an SSH channel, there are no identity or certificate item types, nothing
carries a terminal setting to the renderer, and an item cannot be moved between
vaults at all. Six controls with nothing behind them, listed in
docs/design-import-gaps.md with what ships instead, and none drawn disabled.

The credentials row is marked with ◆ rather than the ⚿ the nav rail uses for the
keychain. U+26BF is outside both faces this application substitutes for the
design's fonts, so it lands on whatever the platform's fallback has; every other
glyph in the pane is from Geometric Shapes, which both carry.

docs/design-import-gaps.md

@@ -116,6 +116,43 @@ the chrome, hosts and terminals, file transfer, the vault, teams, and preference
 > | **Serial** beside **Terminal** in the toolbar | Omitted. Every session here is an SSH channel; a serial transport is not a button, it is a second session kind. |
 > | The strip's tabs inside the titlebar row, with a hamburger | A row of its own under the titlebar. The titlebar already carries the drag region, the search box, the sync light and three window controls, and the strip scrolls — putting both on one 44-pixel row would make the thing that scrolls fight the thing that drags. |
 > | A count on the S3 tab | Omitted. The rail entry it replaces carried one; a number on two of five tabs reads as a fact about those two rather than as the tab's own state, and a terminal tab has nothing to count. The count is on the S3 screen. |
+>
+> ## The desktop's v4 — the host detail pane
+>
+> A fourth pass, narrower than v3: one pane and the cards beside it. It changes the *shape* of the drawer
+> rather than what is in it, and it changes one behaviour that is not cosmetic at all.
+>
+> **The drawer is asked for now.** Selecting a host used to open it, which charged 304 pixels of grid for
+> the act of choosing — including every card arrowed past on the way to the one you wanted. A pencil appears
+> on a card under the pointer, and on the selected card, and that is what opens the pane;
+> `VaultViewModel.IsHostPaneOpen` is the flag, and the context menu has a **Details…** entry so the pane is
+> reachable without a pointer. Once open the pane follows the selection, because a pane about one host
+> beside a grid marking a different one is two answers to the same question.
+>
+> **The pane is three cards, a fixed header and a fixed footer.** Address, General, Connection — the same
+> three in the detail pane and in the host editor, the first as rows and the second as boxes. Only the
+> middle scrolls, so the button each panel exists to offer is never below the fold, which CONNECT could be
+> on a host with fifteen tags. The detail pane's rows are *buttons that open the editor*: the design draws
+> every fact as a filled box, and rather than draw an input that refuses the pointer, pressing one leads to
+> the same card with a real box in it. Saving is a whole-host operation — it validates the key-or-credential
+> exclusion and writes one encrypted payload — so a box committing per keystroke was never on offer.
+>
+> **A host card is two lines and no chips.** The subtitle is `ssh, root, pci, eu-west-1`: the transport, the
+> resolved account, then every tag. It replaces the `user@host:port` line *and* the wrapped row of tag chips
+> below it. The address moved to the card's tooltip rather than nowhere — a card is read while scanning
+> forty machines, where the name and the kind of machine are what is being looked for, and an address is
+> what you read once you have found it.
+>
+> | v4 element | What ships instead |
+> | --- | --- |
+> | **Share this host** | Omitted, as the vault screen's `SHARED WITH · 6` is. A grant is per *vault* and per-item sharing is M5; a button here would imply this one host could be handed over, which is the thing the architecture does not do. |
+> | **Add Telnet**, and **Serial** in the toolbar | Omitted. `ISshConnection` is the only transport there is. This is also why the card subtitle's `ssh` is a constant today rather than a reading — it is stated in `HostRowViewModel.Summary`, which is the one place in this interface where a constant is printed on purpose. |
+> | **+ SSH ID, Certificate, FIDO2** | Omitted. `IDENTITIES` and `CERTIFICATES` have been on this document's list since the first import — neither is even a reserved `SyncEntityType` — and there is no security-key path anywhere in the SSH layer. One control offering three item types that do not exist. |
+> | The **Backspace / Default** row | Omitted. It is a terminal setting, and the client has no preferences store and no frame to carry one to the renderer — see the Preferences section. It would be a control whose value could not survive the window closing. |
+> | The **chevron beside the vault name** | The name alone. An item cannot be moved between vaults: the two are encrypted under different keys, so moving one is a delete and a retype. Where a *new* item is filed is chosen on the keychain screen, which is the only vault question with an answer. |
+> | **Show more ⌄** | Not drawn as a disclosure. What it would hide — notes, the relay switch, forgetting the host key — is in the editor, one press away, and a second fold inside a pane that already scrolls is a second place for a field to be missing from. |
+> | **Port Forwarding** in the sidebar | Nothing, for the third time in this document. |
+> | The host grid's toolbar avatar, share and tag-filter controls | Omitted, as in v3 and for the same reasons. |
 
 Most of it landed. This file is the rest: every element of that design with nothing behind it, which
 project each piece would have to land in, and **what the shipped interface does instead**. That last